1. Field of the Invention
The present invention relates to the isolation and characterization of a novel enzyme which is implicated in the production of sex steroids, and more particularly, to the characterization of the gene and cDNA of a novel 20.varies., 17.beta.-hydroxysteroid dehydrogenase (hereinafter type 5 17.beta.-HSD) which has been implicated in the conversion of progesterone and 4-androstenedione (.DELTA..sup.4 -dione) to 20.varies.-hydroxyprogesterone (20.varies.-OH-P) and testosterone (T), respectively. The use of this enzyme as an assay for inhibitors of the enzyme is also described, as are several other uses of the DNA, fragments thereof and antisense fragments thereof.
2. Description of the Related Art
The enzymes identified as 17.beta.-HSDs are important in the production of human sex steroids, including androst-5-ene-3.beta.,17.beta.-diol (.DELTA..sup.5 -diol), testosterone and estradiol. It was once thought that a single gene encoded a single type of 17.beta.-HSD which was responsible for catalyzing all of the reactions. However, in humans, several types of 17.beta.-HSD have now been identified and characterized. Each type of 17.beta.-HSD has been found to catalyze specific reactions and to be located in specific tissues. Further information about Types 1, 2 and 3 17.beta.-HSD can be had by reference as follows: Type 1 17.beta.-HSD is described by Luu-The, V. et al., Mol. Endocrinol., 3:1301-1309 (1989) and by Peltoketo, H. et al., FEBSLett, 239:73-77 (1988); Type 2 17.beta.-HSD is described in Wu, L. et al., J. Biol Chem, 268:12964-12969 (1993); Type 3 17.beta.-HSD is described in Geissler, WM, Nature Genetics, 7:34-39 (1994). A fourth type which is homologous to porcine ovarian 17.beta.-HSD has recently been identified by researchers Adamski and de Launoit, however, applicant is not presently aware of published information on this type.
The present invention relates to a fifth type of 17.beta.-HSD which is described in detail below.